Microbial community structure in an integrated A/O reactor treating dilutedlivestock wastewater during start-up period
Lijiao Ren , Yining Wu , Nanqi Ren , Kun Zhang , Defeng Xing
DOI:
Received October 29, 2009,Revised November 16, 2009, Accepted , Available online
Volume 22,2010,Pages 656-662
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In order to investigate the correlation between reactor performance and the microorganisms, an integrated A/O reactor was operated
for 72 days to treat diluted livestock wastewater. Chemical oxygen demand (COD) removal e ciency increased from 79% to 94%,
with total nitrogen (TN) removal e ciency from 37% to 50% (HRT 7.4 hr) when the influent COD and TN were ca. 1500 mg/L and 95
mg/L, respectively, and the outlet COD concentration was less than 100 mg/L at the end. Microbial community was monitored during
start-up period by denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA gene. DGGE profiles showed that microbial
community had changed significantly during the start-up and these shifts were in accordance with the reactor performance. UPGMA
clustering analysis showed that 14 anaerobic samples fell into five main groups and so did the aerobic ones, but the grouping patterns
were di erent. Phylogenetic analysis indicated that microbial populations in the anaerobic compartment belonged to Firmicutes,
Proteobacteria, Chloroflexi and Bacteroidetes, while Proteobacteria, Bacteroidetes, Firmicutes, Verrucomicrobiae and Nitrospira were
present in the aerobic compartment. In the anaerobic compartment, more fermentative and acetogenic bacteria were detected during the
start-up while denitrifying bacteria faded away. Two functional populations such as Nitrospira defluvii and Dechloromonas denitrificans
were observed when nitrogen removal was high, indicating that simultaneous nitrification and denitrification occurred in the aerobic
compartment.
